DatagridView Winform ของ VB ใช้ Footer Sum ยังไงครับ

 Dim sumr1 As Integer
        Dim sumr2 As Integer
        For r As Integer = 0 To DataGridView1.Rows.Count - 1
            sumr1 += Me.DataGridView1.Rows(r).Cells(1).Value
            sumr2 += Me.DataGridView1.Rows(r).Cells(2).Value
        Next
        DataGridView1.Rows.Add()
        Dim rrr As Integer = DataGridView1.Rows.Count
        Me.DataGridView1.Rows(DataGridView1.Rows.Count - 1).Cells(0).Value = "ผลรวม"
        Me.DataGridView1.Rows(DataGridView1.Rows.Count - 1).Cells(1).Value = sumr1
        Me.DataGridView1.Rows(DataGridView1.Rows.Count - 1).Cells(2).Value = sumr2

dataGridView1.Rows.Clear()